IL-1 blockade in Schnitzler syndrome: ex vivo findings correlate with clinical remission

Pattern recognition receptors in immune disorders affecting the skin

Pattern recognition receptors (PRRs) evolved to protect organisms against pathogens, but excessive signaling can induce immune responses that are harmful to the host. Putative PRR dysfunction is associated with numerous immune disorders that affect the skin, such as systemic lupus erythematosus, cryopyrin-associated periodic syndrome, and primary inflammatory skin diseases including psoriasis and atopic dermatitis. As yet, the evidence is often confined to genetic association studies without additional proof of a causal relationship. However, insight into the role of PRRs in the pathophysiology of some disorders has already resulted in new therapeutic approaches based on immunomodulation of PRRs.

Schnitzler's syndrome associated with pancreatitis: a disease of IL-1 dysregulation

Schnitzler's syndrome (SS) is a rare inflammatory disease of unknown origin characterized by chronic urticaria and monoclonal gammopathy (usually IgM) associated with at least two of the following components: fever, arthralgia or arthritis, bone pain, hepato- and/or splenomegaly, lymphadenopathy, elevated erythrocyte sedimentation rate, leukocytosis, and/or abnormal findings on bone morphological investigations. To date, about 100 cases have been described with only 4 being reported in the USA. The mean time to diagnosis from the onset of disease is 5.4 years, given the varied symptoms with which patients may present. The pathogenesis of SS remains unknown but likely involves dysregulation of the IL-1 pathway. We describe here a 48-year-old woman with a monoclonal IgM gammopathy and a 3-year history of chronic pruritic urticarial dermatosis, unexplained fevers, chronic polyarthritis, lymphadenopathy, leukocytosis, hepatomegaly, and weight loss. She also had a history of chronic pancreatitis as well as a family history of recurrent pancreatitis. The diagnosis of Schnitzler's syndrome was made, and she was successfully treated with the IL-1 receptor antagonist, anakinra.

The Schnitzler syndrome

The Schnitzler syndrome is a rare and underdiagnosed entity which is considered today as being a paradigm of an acquired/late onset auto-inflammatory disease. It associates a chronic urticarial skin rash, corresponding from the clinico-pathological viewpoint to a neutrophilic urticarial dermatosis, a monoclonal IgM component and at least 2 of the following signs: fever, joint and/or bone pain, enlarged lymph nodes, spleen and/or liver, increased ESR, increased neutrophil count, abnormal bone imaging findings. It is a chronic disease with only one known case of spontaneous remission. Except of the severe alteration of quality of life related mainly to the rash, fever and pain, complications include severe inflammatory anemia and AA amyloidosis. About 20% of patients will develop a lymphoproliferative disorder, mainly Waldenström disease and lymphoma, a percentage close to other patients with IgM MGUS. It was exceedingly difficult to treat patients with this syndrome until the IL-1 receptor antagonist anakinra became available. Anakinra allows a complete control of all signs within hours after the first injection, but patients need continuous treatment with daily injections.

In many aspects, the Schnitzler syndrome resembles the genetically determined auto-inflammatory syndromes involving activating mutations of the NLRP3 inflammasome. This latter point and its consequences will be addressed.

[IL-1 antagonists]

Interleukin (IL)-1 plays an important role not only in the mediation of inflammation but also in the destruction of cartilage and bone. Together with TNF-alpha it is one of the most important cytokines in the pathogenesis of rheumatoid arthritis (RA) and juvenile idiopathic arthritis (JIA). The first IL-1 antagonist to be approved for RA was Anakinra, an IL-1 receptor antagonist. Anakinra appears to be less effective for RA than TNF blockers. Hence, Anakinra is rarely used for the treatment of RA, but more for the treatment of IL-1-mediated diseases such as autoinflammatory syndromes, adult-onset Still's disease and systemic onset JIA. Two newer IL-1 antagonists have recently been approved for the treatment of CAPS (cryopyrin-associated periodic syndromes): Canakinumab, a fully human IL-1beta antibody, and rilonacept, a fusion protein consisting of the ligand-binding domain of the IL-1 receptor and the IL-1-receptor accessory protein, bound to human IgG1. For RA, there is only one proof-of-concept study to date with canakinumab. There are no prospective data for the treatment of patients with RA who did not respond to or tolerate TNF antagonists; in a retrospective analysis, only 8% of anti-TNF pretreated patients achieved an ACR 20 response.

[Adult-onset Still's disease, Schnitzler syndrome, and autoinflammatory syndromes in adulthood]

Adult-onset Still's disease (AoSD), Schnitzler syndrome, and cases of adult-onset autoinflammatory syndromes [10-15% of cases of familial Mediterranean fever (FMF) and tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS)] are characterized by a genetic predisposition, with increased interleukin (IL)-1beta and IL-18 production and TNF-alpha signaling, respectively. As a result, periodic fever and inflammation at barrier tissues (synovial tissues, serous membranes, and the skin) are encountered in such patients. Pathophysiological insights into these diseases have renewed interest in research on IL-1beta in rheumatic diseases and have opened new therapeutic avenues. Recently published studies have shown that patients with Schnitzler syndrome, methotrexate-refractory AoSD, and colchicine-refractory FMF or contraindications to colchicines in FMF respond well to treatment with the soluble IL-1 receptor antagonist anakinra. For TRAPS patients, the p75 TNF-alpha receptor/Fc-IgG1 fusion protein etanercept is the treatment of first choice.

Schnitzler syndrome: response to anakinra in two cases and a review of the literature

BACKGROUND

Schnitzler syndrome is a rare disease characterized by a chronic urticarial eruption and monoclonal gammopathy, as well as clinical and laboratory signs of inflammation. The pathophysiology is still unknown, although various autoantibody-mediated mechanisms have been described. Complete remission of symptoms has been reported recently in patients with Schnitzler syndrome treated with anakinra, an interleukin-1 receptor antagonist.

METHODS

Two patients with Schnitzler syndrome treated with anakinra therapy are presented.

RESULTS

We report two cases of nearly complete remission of symptoms in Schnitzler syndrome after the initiation of anakinra therapy, and the first observation of a relapse under continuous daily anakinra therapy. A review of the published literature on the treatment of Schnitzler syndrome with anakinra is presented.

CONCLUSIONS

Based on published data, monotherapy with anakinra is currently the most promising treatment for Schnitzler syndrome, because it is able to induce complete remission of symptoms.

Autoinflammation: the prominent role of IL-1 in monogenic autoinflammatory diseases and implications for common illnesses

The discovery of the genetic causes of a rare group of immune-mediated inflammatory conditions that mimic infections and allergic conditions in their clinical presentation and the molecular understanding of the function of the mutated molecules in these diseases has led to a revolution in our understanding of the pathogenesis of systemic and local inflammation. The proteins mutated in a number of these so-called autoinflammatory diseases are part of, or regulate the activity of, intracellular molecular complexes, the inflammasomes, that sense "danger" to the body and coordinate an initial immune response. Our understanding of specific triggers of the inflammasomes, coupled with the recognition that inflammasomes are critical for activation of the proinflammatory cytokine IL-1, has provided a rational and very effective target in the treatment of a number of these rare autoinflammatory diseases. In addition, the ongoing discovery of the role of inflammasomes and IL-1 activation and secretion in a number of genetically complex disorders have fundamentally changed our view of disease pathogenesis in a growing number of disorders that were heretofore not even thought of as "immunologic" diseases.

Schnitzler's syndrome with prominent neutrophil infiltration misdiagnosed as Sweet's syndrome: a typical example of urticarial neutrophilic dermatosis

Schnitzler's syndrome is a rare disorder of unknown aetiology characterized by a chronic urticarial eruption, intermittent fever and monoclonal gammopathy. We encountered an interesting patient with this syndrome, who had been misdiagnosed for 10 years as having Sweet's syndrome because of the histopathological picture, which was a prominent perivascular and interstitial neutrophilic infiltrate in the dermis with leucocytoclasia but without vasculitis. An urticarial eruption with this histopathological feature has recently been categorized as neutrophilic urticarial dermatosis, and it is strongly indicative of an associated systemic disease, mainly Schnitzler's syndrome and other inflammatory diseases. We therefore need to be cautious not to confuse Schnitzler's syndrome with Sweet's syndrome. Further, the serum interleukin (IL)-6 levels, but not those of other cytokines and chemokines, correlated with the disease activity in our patient, suggesting that IL-6 may be involved in some of the disease processes, including neutrophil infiltration.

Horror autoinflammaticus: the molecular pathophysiology of autoinflammatory disease (*)

The autoinflammatory diseases are characterized by seemingly unprovoked episodes of inflammation, without high-titer autoantibodies or antigen-specific T cells. The concept was proposed ten years ago with the identification of the genes underlying hereditary periodic fever syndromes. This nosology has taken root because of the dramatic advances in our knowledge of the genetic basis of both mendelian and complex autoinflammatory diseases, and with the recognition that these illnesses derive from genetic variants of the innate immune system. Herein we propose an updated classification scheme based on the molecular insights garnered over the past decade, supplanting a clinical classification that has served well but is opaque to the genetic, immunologic, and therapeutic interrelationships now before us. We define six categories of autoinflammatory disease: IL-1beta activation disorders (inflammasomopathies), NF-kappaB activation syndromes, protein misfolding disorders, complement regulatory diseases, disturbances in cytokine signaling, and macrophage activation syndromes. A system based on molecular pathophysiology will bring greater clarity to our discourse while catalyzing new hypotheses both at the bench and at the bedside.

Differential diagnosis of chronic urticaria

OBJECTIVES

To review diseases that can present with cutaneous signs and symptoms that mimic those observed in chronic urticaria and to discuss the workup necessary to distinguish these diseases from chronic urticaria.

DATA SOURCES

We performed a PubMed search using the following keywords: urticaria, cryopyrin, Sweet syndrome, subacute cutaneous lupus, urticarial vasculitis, urticaria pigmentosa, angioedema, fixed drug eruption, bullous pemphigoid, and reticular erythematous mucinosis. Appropriate chapters in general dermatology textbooks were also reviewed.

STUDY SELECTION

Articles that related to disease states, which present with persistent urticarial lesions, were catalogued for use in this review.

RESULTS

Besides acute, chronic, and physical urticarias, there are 2 categories of diseases that have urticarial lesions. The first group includes those in which the skin lesions are almost indistinguishable from those seen in patients with chronic idiopathic urticaria. Thus, the diagnosis relies on a careful history and physical examination, and in some cases laboratory studies are required. The second group are ones that have skin lesions that at one point in their development have an urticaria-like appearance or on rare occasion may have such lesions. These latter diseases are numerous, and we have tried to highlight the ones that most mimic chronic idiopathic urticaria or are more common.

CONCLUSIONS

A working knowledge of the diseases that can present with urticarial lesions is essential to accurately diagnose and effectively treat these symptomatic and sometimes serious conditions.